docs: def sub(feednames):
      """
      Subscribe to the specified feed(s).
      """
  
      ecode = 0
      current_user_data = contexts.get('anchore_auth', {}).get('user_info', None)
      if not current_user_data:
          current_user_tier = 0
      else:
          current_user_tier = int(current_user_data['tier'])
  
      try:
          for feed in feednames:
              rc, msg = anchore_feeds.subscribe_anchore_feed(feed, current_user_tier)
              if not rc:
                  ecode = 1
                  anchore_print_err(msg)
              else:
                  anchore_print(msg)
  
      except Exception as err:
          anchore_print_err('operation failed')
          ecode = 1
  
      sys.exit(ecode)